A shock absorber includes an outer shell and a piston rod that is slidably inserted into the outer shell. When the piston rod moves relatively to the outer shell in the axial direction, the shock absorber exhibits damping force that suppresses the relative movement of the piston rod relative to the outer shell. Such a shock absorber is used by being interposed between a body and an axle, or between a cabin and the body in a vehicle, for example. Vibration of an object to be damped, such as the body, the cabin or the like, can be suppressed by the damping force exhibited by the shock absorber.
As the shock absorber like this is exposed to the outside for use, dirt, dust and mud (hereinafter referred to as “mud or the like”) are easily adhered onto the piston rod. The mud or the like, adhered onto the outer periphery of the piston rod, is scraped off by a dust seal that seals the outer periphery of the piston rod, when the piston rod enters the outer shell. However, when the mud or the like is dried and adhered onto the piston rod stubbornly, it cannot be scraped off properly by the dust seal. This may facilitate deterioration in oil seal provided on an inner side of the dust seal. For this reason, according to the shock absorber as disclosed in JP2000-81071A or JP2010-175043A, a dust cover that covers the outer periphery of the piston rod is mounted so as to protect the piston rod from the mud or the like.